The previous version of Product had the following:

```
public void setContent(Set<Content> content) {
    this.content = content;
}

public void addContent(Content content) {
    if (this.content != null) {
        this.content = new HashSet<Content>();
    }
    if (!this.content.contains(content)) { 
        this.content.add(content);
    }
}
```